821221 has 8 divisors (see below), whose sum is σ = 864000. Its totient is φ = 779520.

The previous prime is 821209. The next prime is 821263. The reversal of 821221 is 122128.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 821221 - 2¹¹ = 819173 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 821195 and 821204.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (821281) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1605 + ... + 2053.

It is an arithmetic number, because the mean of its divisors is an integer number (108000).

2⁸²¹²²¹ is an apocalyptic number.

It is an amenable number.

821221 is a deficient number, since it is larger than the sum of its proper divisors (42779).

821221 is a wasteful number, since it uses less digits than its factorization.

821221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 539.

The product of its digits is 64, while the sum is 16.

The square root of 821221 is about 906.2124474978. The cubic root of 821221 is about 93.6454502646.

Adding to 821221 its reverse (122128), we get a palindrome (943349).

The spelling of 821221 in words is "eight hundred twenty-one thousand, two hundred twenty-one".